A friend of mine wants to run a Cthulhu game in the dark. What would be a good randomiser to use?

We play fairly rules-light. For example, we could get by with a couple of d6s, or even a couple of tossed coins. Those, of course, don't work in the dark, but they give you an idea of the level of randomness we need. (Not much. And, by the way, don't assume we're using any particular system.)

Have you any ideas? Can you think of anything more interesting than glow-in-the-dark dice?

Ooh. Add a small pinhole lightbox (black cardboard box + LED/flashlight) to the table, and you can ritually place the stone on the pinhole to show the colour. You could use a variety of colours and symbolisms then too: blood red, ichor green, purity white, lightless opaque black, cool blue, alarming yellow…
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SevenSidedDie♦May 26 '11 at 18:10

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You know, black and white stones in a bag, plus a candle (a variation on SevenSidedDie's box), is rather a wonderful solution. Not dark, still atmospheric. Many thanks.
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GrahamMay 28 '11 at 12:53

For a randomizer that can carry a little bit of tension, but can be operated in the dark easily, your group could use a Zippo lighter.

You can arrange it so that it works like a coin toss as a simple Y / N based on whether it lights or not. Success is achieved if it lights (casting away the darkness of fear and uncertainty for a moment) and failure triumphs if it fails to light (sparks of opportunity fade back into the darkness).

NB: Failure can of course be actual failure, or some sort of 'you didn't succeed' challenge, according to how you have arranged to play the session/system. I will just use the terms success and failure in this response for simplicity and sanity.

Method

Players would have one chance to flick the lighter in order to determine success or failure.

To add a little more drama, characters intending to act can take the lighter and open the lid, with that distinctive sound zippos make before making their declarations. Those doing so will have to be as descriptive as possible, their chance to offer a bit to the narration, stating clearly and evocatively what it is that they hope to accomplish.

As an additional tweak, you could offer those who fail a chance to mitigate failure by offering a second chance to flick the flame to life by accepting an additional complication on the result. Repeat as needed up to a reasonable limit, if you like, adding more severe complications with each additional attempt.

Fill half (or more or fewer, depending on desired success rate) with a few beans or coins so that they rattle. Put them in a container. When it comes time to randomize pull an egg from the container and shake it. If it makes noise its a success if not its a failure.

For dependent results remove the eggs from the basket after they are used, for independent results place them back in the basket.

Jellybeans, or any other small snack/candy that comes in various distinct flavors. Choose a different flavor for each type of possible result and mix them all up in a bowl. Probably best not to use more than three or so flavors in the interest of not needing to consult a resolution chart.

When you need a random result a jellybean is eaten, delivering your result in a burst of flavor. You can also modify the odds of any particular result by adjusting the number of jellybeans of each flavor put into the bowl. The eating of the jellybeans will have an effect on the odds as well.

Get some glow-in-the-dark paint from a craft store. Cut a few slips of paper, and paint signs of horror and madness on some. Others leave blank. Players can draw these from a bag or cup during the game—a blank is good, but unfolding the slip to find a sign of horror is a failure/consequence.

Tailor the mix of blanks and signs according to your preferred probabilities, and optionally have a few "steps" of severity to the signs.

The disadvantage with this method is that glow-in-the-dark paint will need to be exposed to strong light for long enough before the game to last the session, and it's easier to misplace the blank slips than the painted ones (though the players will naturally be motivated to not misplace the blanks so they don't tip the scales against them in later draws).

The advantages are that it's low-tech and thematic, and tactile resolution mechanics are always appealing. It's also relatively cheap to set up and easy to customise. With a bit more investment, there are also multiple colours of glow-in-the-dark paint available, broadening the spectrum of results with the addition of "good" glowing signs in addition to or instead of the blanks.

Some kind of glow-in-the-dark spinner. It can be used to select numbers off the spinner or it could be used to select random players, all of whom represent a number (I'm 1, you're 2, Bob is 3, Rae is 4, etc.).

Tying into C. Edward's answer from before, you could also find some of the nasty-flavored beans from either the Harry Potter Bertie Bott's sets or from their Bean Boozled store and mix those in. For a Cthulhu game, those could indicate a loss of Sanity occurs as the character's mind snaps slightly from the stress of the events.